A216446 Palindromic numbers which can be written as the sum of two or more consecutive squares.

5, 55, 77, 181, 313, 434, 505, 545, 595, 636, 818, 1001, 1111, 1441, 1771, 4334, 6446, 17371, 17871, 19691, 21712, 41214, 42924, 44444, 46564, 51015, 65756, 81818, 97679, 99199, 108801, 127721, 137731, 138831, 139931, 148841, 161161, 166661, 171171, 188881

Offset: 1

Author

V. Raman, Sep 07 2012

Keywords

• nonn
• base

Examples

			636 is in the sequence because it is a palindrome and 636 = 4^2+5^2+6^2+7^2+8^2+9^2+10^2+11^2+12^2.
		

Links

• V. Raman and Giovanni Resta, Table of n, a(n) for n = 1..10306 (terms < 10^18, first 298 terms from V. Raman)

Crossrefs

Cf. A034705, A180436, A267600 (terms with more than one representation).

Programs

Mathematica

palQ[n_] := Block[{d = IntegerDigits@ n}, d == Reverse@ d]; upto = 10^6; Union[ Reap[ For[i=1, s=i^2 + (i+1)^2; s < upto, i++, For[j=i+1, s < upto, j++; s += j^2, If[palQ[s], Sow@ s]]]][[2, 1]]] (* Giovanni Resta, Jun 14 2018 *)
With[{nn=200},Select[Union[Flatten[Table[Total/@Partition[Range[nn]^2,n,1],{n,2,nn}]]],PalindromeQ]] (* Harvey P. Dale, Oct 17 2021 *)

Extensions

Errors in previous b-file noticed by Riley Waugh, Jun 13 2018